A deceleration sensor is necessary as means for producing a trigger signal upon occurrence of a vehicle crash and transmitting a trigger signal to passive vehicle occupant protection systems such as air bags, seat belt pre-loaders and other passive vehicle occupant restraint systems. Typically, such a vehicle deceleration sensor is provided with a mass and a displacement sensor which detects movement of the mass by inertia. Since the reliable and precise activation of a deceleration sensor is quite essential for satisfactory performance of a vehicle occupant protection system, a various considerations must be made as to the location for mounting a vehicle deceleration sensor.
Following are primary considerations that should be made in deciding the location for mounting a deceleration sensor:
(1) The location must be able to transmit the deceleration to the sensor without fail and with a minimum time delay;
(2) The location must be as close to the actuator of the vehicle occupant protection system as possible in order to minimize the amount of wiring and ensure the integrity of the wiring in case of a vehicle crash; and
(3) The location must be surrounded in a favorable environment in order to ensure satisfactory performance of the deceleration sensor over its entire service life.
In regards to consideration (1), the deceleration sensor is desired to be mounted on a rigid body member such as front side member, in particular at its front end adjoining a front bumper. However, in this case, the deceleration sensor tends to be remote from the vehicle protection system, and the wires connecting them to each other tend to be more prolonged than desired. Furthermore, the environment is not favorable because the deceleration sensor will be exposed to dust and moisture. In regards to consideration (2) and (3), the interior of the passenger compartment would be a preferred place for mounting a deceleration sensor. However, in this case, since the front part of the vehicle is designed to have buffering effect in case of a vehicle crash by deforming itself and delaying and reducing transmission of impulsive deceleration to the passenger compartment, the deceleration sensor may not be able to detect a deceleration and transmit a trigger signal to the vehicle occupant protection system as quickly as desired.
In view of such problems in regards to the selection for a place to mount a vehicle deceleration sensor, a primary object of the present invention is to provide a mounting structure for a vehicle deceleration sensor which can detect a deceleration indicative of a vehicle crash with a minimum time delay.
A second object of the present invention is to provide a mounting structure for a vehicle deceleration sensor which protects the deceleration sensor from external degrading influences.
A third object of the present invention is to provide a mounting structure for a vehicle deceleration sensor which can place a deceleration sensor sufficiently close to a vehicle protection system which is to be triggered by this deceleration sensor.
These and other objects of the present invention can be accomplished by providing a mounting structure for a vehicle deceleration sensor, comprising a deceleration sensor mounted on a part of a vehicle body where a longitudinal end of a front side member extending along a fore-and-aft direction of the vehicle body on one side thereof and a bulkhead separating a passenger compartment from a front part of the vehicle body are joined together.
Thus, a deceleration resulting from a vehicle crash is quickly transmitted to the deceleration sensor through the front side member through the opening, and the deceleration sensor is protected from adverse environmental effects.
In particular, if the part of the bulkhead is provided with an opening which is communicated with the interior of the hollow front side member, and the deceleration sensor is mounted on the bulkhead with a part thereof projecting into the interior of the hollow front side member, the deceleration sensor would not protrude into the passenger compartment.
According to a particularly preferred embodiment, the deceleration sensor is provided with a mounting flange which is attached to a peripheral part of the bulkhead around the opening, and a protective cover covering the part of the deceleration sensor projecting into the interior of the front side member and having a flange which is clamped between the peripheral part of the bulkhead and the mounting flange of the deceleration sensor. Thus, the deceleration sensor is securely protected from intrusion of dust or moisture without complicating the process of manufacturing and assembling the deceleration sensor.